It is demanded that an automotive internal combustion engine fulfill requests concerning various performance characteristics such as drivability, emissions performance, and fuel consumption rate. The requests concerning the various performance characteristics are issued from an overall vehicle control device to an internal combustion engine control device. The internal combustion engine control device controls control amounts of the internal combustion engine in order to fulfill such requests. However, it is difficult to fulfill all such requests completely and simultaneously. Therefore, it is necessary to devise a scheme for successfully making the various requests be reflected in the control amounts of the internal combustion engine.
Examples of such a scheme are disclosed in JP-A-2009-162199 and JP-A-2008-169825. Internal combustion engine control devices described in JP-A-2009-162199 and JP-A-2008-169825 perform a request mediation process to make various requests be reflected in the control amounts of the internal combustion engine. In the request mediation process, at first, each request is expressed by a predefined physical quantity. The physical quantity is used as a control amount for the internal combustion engine. The physical quantity includes, for instance, a torque, an efficiency, or an air-fuel ratio. The efficiency is the ratio of an actually output torque to a torque that can be potentially output from the internal combustion engine. Next, request values expressed by the same physical quantity are collected. One value is then determined from a plurality of collected request values in accordance with predetermined calculation rules. This determination process is referred to as mediation.
The calculation rules for mediation can be set up as desired. However, if the calculation rules are inappropriate, only requests having relatively high priority may be reflected in a final mediation value, that is, a target control amount value, while requests having relatively low priority are left unreflected. To properly control the internal combustion engine, it is necessary to make not only requests having relatively high priority but also requests having relatively low priority be reflected as appropriate in the target control amount value.
As regards the above matter, an effective solution is described in JP-A-2009-162199. A mediation method disclosed in JP-A-2009-162199 does not express a request with one numerical value, but expresses it in the form of a request value range and of an expected value distribution indicative of the degree of expectation of each request value within the request value range. The sum of expected values of all requests expressed by the same physical quantity is then calculated. Eventually, a request value that maximizes the sum is calculated as the mediation value, that is, the target control amount value. When the above-described mediation method is used to determine the target control amount value, all requests including those having relatively low priority can be reflected in the target control amount value in accordance with their importance.
In the above-described “request mediation,” it is assumed that requests to be mediated are expressed by the same physical quantity, or more precisely, expressed by a physical quantity used as a control amount. Therefore, it is necessary that all requests issued from a vehicle control device to an internal combustion engine control device be expressed in the form of a requested control amount value. However, using the form of a specific requested control amount value may not always be appropriate depending on the type or description of a request. In such a case, a request may not be properly reflected in a target control amount value.